Human Anatomy

THE SKELETAL
Skeletal system includes

BONE: mineralized connective tissue

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Functions of the skeletal system
– Support: forms a rigid framework to which the
softer tissues and organs of the body are attached.
– Protection: encloses and surrounds the vital
organs of the body by forming cavities. E.g., rib
cage, skull, pelvic cavity, vertebral column.
– Body movement: helps to move the body by
giving attachment to skeletal muscles.

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 Functions cont…
– Hemopoiesis: the red bone marrow of an adult
produces red blood cells, white blood cells and
platelets.
– Mineral storage: about 95% of the calcium and
90% of the phosphorus in the body are deposited
with in the bones and teeth.
– Lesser amounts of magnesium and sodium salts
are also stored in bone tissue.

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 Divisions of the skeletal system.
• Consists of 206 bones in the adult
• It is divided into
– the axial (80)
– the appendicular (126)
1 THE AXIAL SKELETON
– consists of the bones that form the axis of the body
– Form skeleton of the head, neck and trunk.
Auditory ossicles (6)
– malleus
– incus
– stapes
Hyoid bone (1)
– located above the larynx and below the lower jaw.
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(A) Lateral view
The Skull (22)
consists of cranial bones and facial bones.
The cranial bones
8 in number.
The facial bones
14 in number.

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 CRANIAL BONES
– Most bones of the skull are joined
by rigid sutures
– These include:
1. Frontal bone
- Forms the anterior roof of the
cranium, the forehead
2. Parietal bones(2)
– forms the upper sides and roof of
the cranium.
3.Temporal bones(2)
•Forms the lower sides of the cranium.

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4. Occipital bone
• forms the back and much of
the base of the skull.
5. Sphenoid bone
•forms the anterior base of the
cranium.
– It is butterfly-shaped with
outstretched wings.
6. Ethmoid bone
• forms the roof of the nasal
cavity.

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Facial Bones(14)
– with certain cranial bones (frontal and portions
of the ethmoid and temporal bones) provide
the basic shape of the face.
– support the teeth and provide attachments for
various muscles that move the jaw and cause
facial expressions.

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Facial Bone…
– All are paired except the vomer and mandible.
It includes:
– Maxillae
– Mandible
– Palatine bones
– Zygomatic bones
– Lacrimal bones
– Nasal bones
– Vomer
– Inferior nasal conchae
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 Sutures
Meaning to stitch, are immovable joint found
between skull bones. There are four main sutures
in the skull.
a) Coronal suture: between the frontal & the two-
parital bone.
b) Sagital suture: between the two parietal bones.
c) Lambdoidal suture: between parietal &occipital
bone.
d) Squamosal suture: between parietal bone and
temporal bone

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 Fontanels
• The skeleton of a newly formed embryo consist cartilage
or fibrous membrane structures, which gradually
replaced by bone the process is called ossification.
• At birth membrane filled spaces on the skull are called
fontanel. They are found between cranial bones.
The Anterior (bregma) fontanel, between angle of two
parietal bones & segment of the frontal bone. It is
diamond shaped and is the largest fontanel. It closes 18 to
24 months after birth
b) The posterior (lambda) fontanel, between parietal &
occipital bone. It is also diamond shaped but smaller than
the anterior fontanel. It closes 2 months after birth.
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Function
•They enable skull of the fetus to compress as
it pass through the birth canal
•Permit rapid growth of brain during infancy
•Serves as a landmark (anterior fontanel) for
withdrawal of blood from the superior sagital
sinus
•Aid in determination of fetal position prior to
birth.

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The vertebral column(26)
– composed of 33 individual vertebrae;
in infant
– 7 cervical, 12 thoracic, 5 lumbar,
– 5 fused sacral but in adult fused and form one
– 4 or 5 fused coccygeal vertebrae, but fused during
adult
– of which 26 are moveable and the rest are fused.
Cervical Vertebrae
• The seven cervical vertebrae, identified as C1–C7,
are the smallest, lightest vertebrae.
• The first two cervical vertebrae are the atlas (C1)
and the axis (C2)
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 Thoracic vertebrae
– serve as attachment of ribs to form the posterior
anchor of rib cage.
– They are larger than the cervical vertebrae and
increase in size from T1 to T12.
Lumbar vertebrae
• identified by their heavy bodies, thick blunt spinous
processes for attachment of powerful back muscles.
Sacral vertebrae
– consists of 5 fused bones;
– fuses between puberty and ages 25–30
– protects reproductive, urinary, and digestive organs

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 Normal curvature
• The cervical and lumbar curvatures are con-
cave posteriorly, whereas the thoracic and
sacral curvatures are convex posteriorly.
• These curvatures increase the resilience of the
spine, allowing it to function like a spring
rather than a straight, rigid rod.

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The Rib Cage
• This consists of the
– 12 paired ribs, costal cartilages and
– the sternum.
• It supports the pectoral girdle and upper limbs,
protects and supports the thoracic and upper
abdominal viscera, and plays a major role in
breathing.

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• Sternum (breast bone)
– an elongated, flattened bony plate
– consist of three separate bones:
• manubrium (upper part),
• the central body, and
• the lower xiphoid process.
– The sternal angle is an elevation between the
manubrium and the body of the sternum at the
level of the second rib.

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• Ribs
– There are 12 pairs, each pair being attached
posteriorly to a thoracic vertebra.
– Anteriorly, the 1st seven pairs are anchored to
the sternum by individual costal cartilages and
are called true ribs.
– The remaining five pairs (8,9,10,11 and 12) are
termed false ribs

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Ribs cont…
– The last two pairs of false ribs (11 and 12)
do not attach at all to the sternum, and are
called floating ribs.
– Spaces between the ribs are called
intercostals spaces which are occupied by
intercostal muscles

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 The Appendicular Skeleton
Pectoral Girdle
– Clavicle (collar bone).
• Binds the shoulder to the axial skeleton and
• positions the shoulder joint away from the
trunk for freedom of movement.
• This forms the sternoclavicular joint medially
with the sternum
- Scapula (shoulder blade)
• a large, triangular flat bone positioned on the
posterior aspect of the ribcage,

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Brachium (arm): 1 each
This extends from the shoulder to the elbow and
contains a single bone, the humerus.
Humerus
 the longest bone of the upper limb.

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Antebrachium
(Forearm): 2 each
– Bones of the forearm
include the
• Ulna on the
medial side, and
• The radius on the
lateral (thumb)
side.

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The Manus (Hand)
– The each hand contains 27 bones,
constituting the carpus, metacarpus and
phalanges.
• Carpus (wrist 8 bones each )
– The wrist consists of eight carpal bones
– Arranged in two transverse rows of four
bone each
– The proximal row, from lateral to medial
side, consists of
– The scaphoid, lunate, triquetrum , and
pisiform bone.
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 – The distal row, in the same order, includes the
trapezium bone, trapezoid, capitate, and
hamate bone.
Metacarpus (palm 5 bones each)
• The metacarpal bones are named I to V from
lateral (thumb) to medial side.
• Phalanges:(14 bones each)
– Arranged in a proximal, middle and a distal
row

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 Pelvic Girdle
– is formed by two hip bones and sacrum &
coccxy
– united anteriorly by the symphsis pubis.
– It is attached posteriorly to the sacrum of the
vertebral column. .
– Each hip bone consists of three separate
bones:
– the ilium, the ischium, and the pubis,
which fuse in the adult

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Thigh
Femur (thigh bone):
– This is the only one bone of the thigh.
– It’s the longest, heaviest, strongest bone in the
body.
Patella (kneecap)
– a triangular sesamoid bone.
– The patella protects the knee joints

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 Leg
Tibia (Shinbone)
• articulates proximally with the femur at the
knee joint to bear the weight of the body&
distally with the talus of the ankle.
Fibula
– It is a long, narrow bone
– more important for muscle attachment than
for support.

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Foot (26 bones)
– The foot contains 26 bones,
– constitute the tarsus, metatarsus, and phalanges.
Tarsus (7)
– consists of seven tarsal bones.
Proximal group: Talus and calcaneus
– The calcaneus is the largest of the tarsal bones
and provides skeletal support for the heel of the
foot.

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Intermediate group: Navicular bone.
Distal group: from medial to lateral side, the
medial cuneiform, intermediate cuneiform, and
lateral cuneiform bones, and the cuboid bone.

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Metatarsus(5 bones)
– composed of five metatarsal bones, numbered I
to V from medial to lateral.
Phalanges(14 bones)
– are the skeletal elements of the toes,
– arranged in a proximal(5), middle(4) and a
distal(5) row as with those of the hands.
– The great toe (hallux) has only a proximal and a
distal phalanx

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